Various attempts have been made to develop commercially viable six axis joysticks. The complexity of the prior art designs has resulted in expensive products which may be only affordable for computer aided design and other high value industrial and commercial applications. The “SpaceOrb®”, which was developed by Spacetec IMC Corporation and marketed as a computer gaming peripheral device for several years during the late 1990's, was ultimately discontinued, perhaps due to its complexity and manufacturing cost relative to its roughly $50 to $100 retail price. Patents related to the Spacetec SpaceOrb® which were assigned to Spacetec IMC Corporation as of date of issue include U.S. Pat. No. 5,591,924 to Hilton, U.S. Pat. No. 5,706,027 to Hilton et al, and U.S. Pat. No. 5,798,748 to Hilton et al. Hilton was also granted an earlier patent in the same field, U.S. Pat. No. 4,811,608, assigned as of date of issue to Spatial Systems Pty Limited. The six axis devices currently offered by Logitech (which may have purchased Spacetec IMC Corp) include the Spaceball® and Spacemouse®, the January 2002 retail prices of which were approximately $500 each.
Other attempts have been made to use optical position transducers in a six-axis device. For example, U.S. patent application Ser. No. 20010038380 to Salcudean et al discloses the use of light sources and sensors mounted to both the stationary and movable elements of a joystick. Such a scheme may entail unnecessary complexity of construction and may result in a less reliable and less robust device due to the requirement for movable electrical components requiring flexible connections.
Many other methods have been utilized to achieve six axis or multi-axis control. For example, multi-axis input devices have also been built around conventional metal foil strain gage technology and also using wire strain gages. Such devices may essentially be force input devices and may fail to provide the operator with any useful deflection feedback. The primary signals from such devices may require careful shielding and subsequent amplification to compensate for the inherently low gage factor of the strain gages.
U.S. Pat. No. 4,876,524 to Jenkins and U.S. Pat. No. 5,767,840 to Selker are examples of prior art in which the use of strain gages is disclosed. The use of such strain gages may be complicated by temperature-induced errors and low gage factors, both of which can add to the difficulty of signal processing and signal shielding. Furthermore, the allowable strain may be barely perceptible to the operator, and may result in a lack of useful and desirable deflection feedback to the operator. Furthermore, the low strains may preclude the use of mechanical stops to prevent overloading the strain gages. Strain gages may be sized to include a factor of safety with respect to loads which may decrease their already poor gage factor even further. Even with a factor of safety, the devices using strain gages may be unsuitable for applications such as computer games, which may often be dropped on the floor by children.
Other six axis joystick designs of prior art utilize a plurality of linear variable differential transformers, variable inductors, or other linear discrete mechanical displacement transducers. Some of these six-axis input devices have been based on spring centered LVDT's (linear variable differential transformers) in a Stewart platform configuration. Such devices may be expensive and fragile in comparison to the economical and robust construction of a 6 axis input device built in accordance with the present invention. The multiple mechanical joints of the prior art may result in a trade-off between precision and cost.
An example of a simplified device of the Stewart platform variety is disclosed in U.S. Pat. No. 6, 329,812 B1 to Sundin, wherein the important consideration of cost is addressed. Overall complexity may not be avoided, however, because of the need to shield radio frequency interference and because of interference effects between adjoining inductive springs. A further disadvantage of the Sundin design may be that the multiple springs could result in an assembly that is subject to unacceptable resonant vibrations if used in association with construction equipment or moving vehicles. Such vibration may include resonance of the active grip on its spring(s) or may involve lateral or higher mode vibrations within the springs themselves.
Yet another known six-axis joystick may be comprised of a plurality of magnetic sensing coils and multiple movable magnets. Examples of patents disclosing magnetic position detection include U.S. patent application Ser. No. 20010055002 to Endo and U.S. Pat. No. 5,687,080 to Hoyt et al. These designs may often be much more complex and expensive than the present invention and may not provide any inherent shielding from ambient magnetic flux
Yet another method is the coupling of two three-axis controllers to attain six axes control as disclosed in U.S. Pat. No. 5,749,577 and U.S. Pat. No. 6,033,309 to Couch et al. Such a method may be more expensive than the present invention and may lack an intuitive six-axis interface.
The large size of many of the devices built in accordance with prior art may result in unintended and undesirable coupling between the horizontal axis of rotation and the horizontal axis of translation. Such coupling may require subsequent diagonalization by means of signal processing with a corresponding loss in precision and dynamic range of the device. Such undesirable coupling may have been difficult to avoid in the prior art because of the expense and technical obstacles, which the required miniaturization of such prior art designs may entail.
The transducer systems of the six axis joysticks of the prior art may have generally been physically too large or heavy for many applications such as incorporation into keyboards or hand held computers, for positioning as extensions of other control handles or grips, or for enclosing near the center of the user's hand within a conventional joystick such as that disclosed in U.S. Pat. No. Des. 381,701 to Salinas.
The need for hand stabilization during trackball use while operating an aircraft has been recognized. Dassault Aviation has adapted a conventional two-axis track ball to include a palm rest to facilitate reliable (two axis) cockpit display cursor control under turbulent flight conditions (PROFESSIONAL PILOT magazine/January 2002). Six axis devices of the prior art may be too bulky to incorporate within such a palm rest. In fact, many six axis input devices of the prior art may have been so bulky that they no longer resemble sticks and may have therefore not even been referred to as “joysticks”.
Various multi-axis input devices or “joysticks” that utilize some form of magnetic field measurement such as Hall effect sensing are known. Examples of patents related to multi-axis input devices or joysticks which disclose Hall Effect sensing include U.S. Pat. No. 5,959,863 to Hoyt et al and U.S. Pat. No. 5,687,080 to Hoyt et al. U.S. patent application Ser. No. 2001/0055002 to Endo also discloses the use of Hall Effect sensing for multi-axial computer input devices.
Several articles on the subject of six axis user interfaces by Shumin Zhai, Ph. D. have been published. These include: Human Performance in Six Degree of Freedom Input Control, Interaction in 3D Graphics, and User Performance in Relation to 3D Input Device Design.
It is an object of this invention to provide a low-cost robust alternative to current multi-axis computer input devices. In particular, an object of this invention may be to provide a device sufficiently low in cost to be attractive for use in conjunction with computer games, and the like, as well as sufficiently simple and robust for use in, but not limited to, industrial applications. Currently available devices may be prohibitively high priced for the computer gaming industry and may be too fragile for a typical construction equipment application. The present invention, in contrast, may require only two moving parts, which can be a simple coil spring and a simple plastic knob with an internal reflective surface, for example. The plastic knob of the present invention may have about the same manufacturing cost as an ordinary flashlight reflector. The overall manufacturing cost of the present invention may be significantly lower than the manufacturing cost of any other prior art six-axis joystick and may be in fact lower than the manufacturing cost of typical two axis joysticks.
A further object of this invention may be to provide a simple easy-to-manufacture 6-axis computer input device, consisting of as few components as possible. The preferred design may incorporate all, 7 for example, transducers onto a single printed circuit board or into a monolithic electro-optical package.
Another object of this invention may be to provide a high quality and high precision signal by optimally locating a high-resolution transducer element with respect to the grip and the user's hand and wrist to yield well conditioned transform equations.
Yet another object of this invention may be to provide a durable, robust multi-axis input device suitable for such applications as control of machinery and construction equipment, and the like.
A further object of this invention may be to allow greater control in industrial and construction equipment applications in general, where multi-axis controls may have been technically deficient and commercially unattractive.
Another object of this invention may be to provide a transducer element of sufficiently small size that it can be centrally located within the handle of a gaming joystick, in line with the parallel-to-the-Ulna-and-Radius-bones axis of wrist rotation instead of below said axis, as may often be the case for prior art designs.
A further object of this invention is to provide a transducer element which may be of sufficiently small size to permit easy finger-tip manipulation of the active grip, while leaving space within the user's hand for a stationary grip element or a palm rest which may be needed to stabilize the user's hand and arm so that the multi-axis joystick functions can be safely used in moving vehicles on land, in water, in air or in space.